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Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support debug_dma_m

To: shuah.khan@hp.com
Subject: Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support debug_dma_mapping_error
From: David Daney <ddaney.cavm@gmail.com>
Date: Fri, 26 Oct 2012 13:07:02 -0700
Cc: ralf@linux-mips.org, kyungmin.park@samsung.com, arnd@arndb.de, andrzej.p@samsung.com, m.szyprowski@samsung.com, linux-mips@linux-mips.org, LKML <linux-kernel@vger.kernel.org>, shuahkhan@gmail.com
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On 10/26/2012 10:06 AM, Shuah Khan wrote:
On Fri, 2012-10-26 at 09:45 -0700, David Daney wrote:
On 10/26/2012 09:01 AM, Shuah Khan wrote:
Add support for debug_dma_mapping_error() call to avoid warning from
debug_dma_unmap() interface when it checks for mapping error checked
status. Without this patch, device driver failed to check map error
warning is generated.

Signed-off-by: Shuah Khan <shuah.khan@hp.com>
---
   arch/mips/include/asm/dma-mapping.h |    2 ++
   1 file changed, 2 insertions(+)

diff --git a/arch/mips/include/asm/dma-mapping.h 
b/arch/mips/include/asm/dma-mapping.h
index be39a12..006b43e 100644
--- a/arch/mips/include/asm/dma-mapping.h
+++ b/arch/mips/include/asm/dma-mapping.h
@@ -40,6 +40,8 @@ static inline int dma_supported(struct device *dev, u64 mask)
   static inline int dma_mapping_error(struct device *dev, u64 mask)
   {
        struct dma_map_ops *ops = get_dma_ops(dev);
+
+       debug_dma_mapping_error(dev, mask);
        return ops->mapping_error(dev, mask);
   }



Although this is a start, I don't think it is sufficient.

As far as I can tell, there are many missing calls to debug_dma_*() in
the various MIPS commone and sub-architecture DMA code.

Really you (or someone) needs to look at *all* the functions in
arch/mips/asm/dma-mapping.h, and arch/mips/mm/dma-default.c and find
places missing a debug_dma_*().

Is it correct to assume that this patch is not needed on MIPS until
debug_dma interfaces get added to MIPS common and sub-architecture DMA
code.

No, you have a false predicate here.

debug_dma_* *is* already mostly added. The problem is that it is incomplete. That is the nature of the problem. Your patch makes it slightly better, but doesn't fully fix the problems.



When I didn't see dma_map_page() in arch/mips/include/asm/dma-mapping.h
defined, and just an extern, I incorrectly assumed, it is getting picked
up from <asm-generic/dma-mapping-common.h>, hence the need for this
patch in the first place.

-- Shuah





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